Pelagian Rebreather Course… a simple deconstruction


This is the tale of the first North American Pelagian air-diluent diver course. I’m unsure whether the three participants (Dave Taylor, a doctor from Rochester, New York, Erik Van Dorn, CFO of a large construction firm and also from New York, and me, neither from New York nor smart enough to have a real job) are early adopters or misguided rebreather Luddites. But in the final analysis, none of that really matters. The course was eventful… and enjoyable.First of all, the course scheduling demons had played havoc with the execution of our course. Pelagian instructors are thin on the ground: I know of only about six world-wide. Ours was a mate of mine from Northern Ireland. Our third attempt at it had us diving during the first week of November in the Thousand Islands region, which is on the Canada / US border where Lake Ontario, the last of the Great Lakes, empties into the St. Lawrence River. Ask me generally about doing courses in this location at this time of year and there’d probably be a couple of expletives in my reply.

Don’t get me wrong, Fall is great in central North America, but November anywhere in the Great Lakes Basin can be bitterly cold, windy (the gales of November, right) and generally miserable. Planning course work in the area in November is always a crap shoot and the thought of a minimum of two hours a day in the water and the potential of surfacing with blowing snow in the air was not a great confidence builder. However, we lucked out and had sunshine, high teens and low twenties for air temps and water on most dives around 11 or 12. (The River unlike the Lakes rarely has waves taller than knee high so we also had no blow-outs or rough conditions to deal with. The only exception was Saturday morning’s dive which was our last… and it was conducted under grey skies and light rain… easy!)

A quick word about the overtext for this class. I am not sure how much you know about rebreathers in general. Simply put they are nitrox gas mixing machines which re-circulate breathing gas while removing carbon dioxide (bad gas) and replacing it with fresh oxygen (good gas)! In many units the addition of oxygen is computer controlled, but the Pelagian is a completely diver controlled closed-circuit rebreather (DCCCR). There are no electronics governing the partial pressure of oxygen in the diver’s breathing loop. The diver controls this him or herself, manually with an “add button” which simply purges pure oxygen into the gas on the inhalation side of the loop, and by means of an adjustable needle valve assembly, which serves to automate the process somewhat at depth. Oxygen partial pressure is monitored by a couple of fuel cells situated in the head of the scrubber unit. Their reading is displayed on a simple gauge which can be worn on the diver’s wrist or be clipped to the diver’s harness. The unit is very compact, can accommodate almost any sized cylinder for diluent (air in our case) and oxygen, and is commonly worn with a traditional cave-diver’s backplate, wing and harness. Everything about the setup including work of breathing at depth was great. For additional security, we carried an open circuit bailout system which is a stage bottle complete with SPG, first and second-stage regs and in my case, a low-pressure inflation hose for wing inflation.

And a quick word about me. I work for a dive education agency and teach for a living. For me to be on the receiving end of a diver-level course is a rare treat and a multi-level learning experience since I am professionally engaged to assess the instructor’s teaching style as well as needing to learn as a student. As an aside, I was Dave and Erik’s Advanced Trimix Instructor on Open Circuit. Needless to say, this made the classroom dynamics interesting.

I picked our instructor, Stephen Phillips, up from Toronto’s Pearson Airport late Tuesday lunchtime. He was a little early and we missed rush-hour traffic across the top of the city arriving at our hotel in Rockport about an hour ahead of schedule. Dave and Erik were already there and over supper that evening, we chatted about the course and what would be expected of us.

At the core of a rebreather program is the need for students to demonstrate a cautious approach to diving the unit. Any underwater adventure carries risk but CCRs bring a whole new category of challenges to the picnic table. These new and enhanced risks include toxicity from too much oxygen, toxicity from too much carbon dioxide and unconsciousness from too little oxygen. I knew that both Dave and Erik are cautious and contentious technical divers… but also realized that this is not necessarily the optimal starting point for learning the basics on a rebreather! Like me, they had many habits to unlearn.

Our first full day together was brilliantly sunny and warm. It was spent doing some basic classroom stuff, assembling units (all three of us had oxygen and dil in 6 litre aluminum luxfers), making the necessary adjustments and setting off for a local waterside park about 15 minutes away in Brockville. Our first task was trying to get our weighting squared away.

As a team. we found weighting a special challenge. The unit needs less ballast than most CCRs but all the information we’d gathered – from various sources including the guy who designed the units – did not translate cleanly to drysuit diving. Bottom line seems to be that for nobs like us, a steel backplate and about four to five kilos of lead works well with trilam suits and Fourth Element Arctic undies.

Once we had that sorted, we ventured into the vast depths (about four metres) to work through basic operations on the unit and some simple tasks such as buoyancy, trim and staying alive. I had an advantage over my classmates because of some experience with semi-closed rebreathers and other CCRs. Plus I had spent an extra day and a half with our instructor earlier in the summer. But none of us was immune to newbie missteps. Dave for example seemed determined to go “swim-about” which understandably made our instructor have kittens. After a few words though, we settled into something resembling a working tempo and proceeded to go through a long check list of drills on the units.

I immediately felt at home on the unit. Certainly the streamlined design of the counter-lungs and the positioning of the various loop connections helped keep our configurations clean, and the biggest initial challenge after weighting was how to load up a 6 L bailout bottle at the beginning of the dive without help. (We had this down pat by the end of day three but day one was agonizing!)

After day one, I was impressed with the concept of DCCCR. For an experienced OC diver, it seems somehow more natural to control the oxygen level manually and once minimum loop volume is kind of mastered, driving the gas, establishing something like a balance between buoyancy and gravity, and staying conscious engaged only about 90 percent of my awareness!

Day Two and another sunny morning spent changing bits and pieces of kit… Drings underneath the counter-lungs are about as useful as ashtrays on a motorcycle, so they were the first things to undergo metamorphosis. I also added a second, second stage to my bailout cylinder… one worn around my neck and held in place by a necklace – very much like the secondary reg carried for years on my OC rig – the second bungied to the tank ready for those complete failure drills I suspected would happen at some point… Regardless of the potential additional drills our instructor might have in store for us… particularly me… I was sure that I am not ready to buddy-breathe from a bailout cylinder while wearing a CCR.

Anyway once all the frittering was done, we headed back to the water. The spot we worked in was perfect for us to stay focused on running the units and practicing drills… very few distractions, no current, decent visibility (notwithstanding a few fin drags… actually, getting horizontal in the unit was a cinch and I take full responsibility and make no excuses for the John Deere award Erik presented me with at the end of the day).

We worked until late afternoon on diluent flushes, cell validations, simulated problems with oxygen levels, various failures and toddled around scaring bass and small sunfish. Another couple of hours on the units and I was beginning to feel where the loop volume should be to facilitate gas circulation and control of buoyancy. I was still making the occasional mistake thinking that my lung volume will have an effect on buoyancy, but started to feel less engaged with the unit and more so with actual diving… which must be progress. One huge advantage over OC very apparent at this point is the lowered thermal stress. After a couple of hours spend in chilly water which on OC would have me a little chilled, I was finishing dives feeling toasty.

The next hour or so was a blur of activity… Fills, rinses, reassembly and supper in the local pub. All good stuff and the dawning of Day Three saw us all bright-eyed and bushy-tailed heading into Brockville for a visit to the bank (bloody Canadians were giving me no premium for US dollars… ironic since I was the only one who arrived with nothing but US cash and am also the only Canadian in the bunch)! While there, we had breakfast in Taitt’s Bakery… breakfast burritos… and then headed to our dive spot.

The plan for Day Three was to venture into slightly deeper water and this required a lengthy swim. I lead and hooked up with the line from shore out to a small wooden wreck sitting near the main channel… the St. Lawrence Seaway… passing freighters sound different on a CCR!

The current was slight and the swim an easy 20 – 25- minute kick. The deeper water skills included more structured use of the oxygen flow meter, which is brilliantly simple and worked like a charm. We all got it dialed in and performing as it’s supposed to. The drills on this day were more complex… multiple things to attend to and the focus was on dealing with problems while maintaining the loop. The one thing that’s a drag is running the unit semi-closed (taking a few breaths then venting gas from the loop into the water and then activating the Automatic Diluent Valve which added fresh air to the loop. This exercise is one way around a depleted oxygen supply and is a pain in the rear but at the point we were doing this we were heading back to shallower water and the “skills” platform, so I put up with it.

Now, deploying a DSMB on a rebreather presents a whole different set of issues, but my buddies and I managed to get our markers to the surface with a minimum of muppetry. I saw Stephen cross himself only twice during the exercise, and took that as a sign there’s been a marked improvement over earlier attempts. One of which had me snorting with laughter.

We finished in good time and headed back to Dive Tech… likely one of the best shops in this region of North America and certainly a boon to us at all stages of our course (Thanks to Dan, Beth and the dive staff). Exam night but first we quickly prepped the units for a deeper “final” dive on Saturday (maybe two dives), and headed back to the hotel in failing daylight… This was our best day yet.

No real issues with the exam… but during our run-through with Stephen later that night, we all have suggestions for future Pelagian courses and some comments on a few questions… I put this down to Andy’s core experience being in a wetsuit and warmish water and not in Great Lakes conditions. For example, RMVs here are higher and consequently critical gas volumes for bailout are higher… essentially, as a group we decide that a fully charged 6 L bailout is the minimum-sized security blanket any of us will dive with. Our scenario in fact required us to plan a dive with our bailout bottles containing no less than 670 litres of gas on hand for each CCR diver. In any event, bull**** baffled brains and we all passed!

Overnight, someone in the weather office flicked a switch and we woke to cooler temperatures, overcast skies and rain. Our plan was to get in a one-hour dive before breakfast and then review the situation. The dive spot was within a two-minute drive of the hotel and we were doing bubble checks before anyone else in the area was up and about.

The dive went exceptionally well. The site was different to our previous dives and we were able to hit target depth quickly and swam along the base of a rock wall covered in freshwater sponges and dotted with bass and the occasional catfish. The skills required of us were to actually dive and follow the plan we had created the previous evening.

By this point in our development as CCR divers, we had all begun to get the feel of the unit. My lasting impression was that the work or breathing on the unit was very low and maintaining loop volume was part science and a lot of art both tempered by a slow, methodical approach. Adjustments to buoyancy via wing and suit have to be much more controlled than with OC. However, once buoyancy is set, it remains rock solid. I thought we all looked pretty good swimming along… back-finning, doing turns, avoiding each other and old dock work like pros.. Well at least like beginner CCR divers.

The only wrinkle was Dave’s stomach and we turned about five minutes early than planned to head back to the exit point… or a point that looked similar but which actually was a surface swim away from the actual exit point. Our ascent was slow, controlled and “safe.” (I am told the sharp stabbing pains are normal and they went away after a few days!)

Once on the surface, Stephen shook a few hands and we called it a day in time to go back to the hotel, change and head into the local café for a tea and a toasted western. I think we arrived back at Dive Tech before 10 am.

Some thoughts on the course and Pelagian… I learned a lot, and will incorporate some of those things learned into courses I teach in future. A special thank you to Stephen, Dave and Erik for their contributions to a great experience. It was challenging and it was a week spent doing some very worthwhile training. At the end of a few days, we are getting comfortable with basic operations within the limitations of our comfort zone and so on… so lots to go on that score.

My personal take on the whole DCCCR philosophy is very positive. I like being completely in control of my oxygen partial pressure. One observation is that the learning curve towards being ready for staged deco will be steeper than on a computer-controlled unit simply because maintaining a setpoint is harder. (A little sidebar here. Since control and stabilization of the oxygen partial pressure is key to working out actual decompression stress, it will be a while before I feel comfortable planning dives beyond the NDL on this unit.)

The unit itself is very compact. It took all of about 30 minutes to begin getting comfy with the position of various controls and less time to attain some control of buoyancy and trim… this can be put down to the position of the lungs (along the side of the diver’s body), the way the tanks are slung (just like a set of doubles) and the flexibility inherent in building your unit from a “kit” which means you dictate things like hose lengths and position of attachment points on the harness. Thanks to Andy for that.

Hope this ramble helps someone. Certainly if you’re thinking about DCCCR feel free to contact Dave, Erik or me… we may be able to give you some advice.

One final point… a few people have contacted me and asked why I’ve “moved away” from an electronically controlled CCR. Actually, I have not moved away from anything. My belief is that diving one unit is not a put down of any other unit. They each have different strengths and weaknesses and each is the right tool for a specific application. My original interest in Andy’s unit was triggered by its simplicity and its potential for packing down into a small carry-on package for air travel. At the end of the course, its further attractions are how wearing the unit was really not much different to wearing my basic cave/technical kit configuration… except for the obvious reduction in overall mass…


8 thoughts on “Pelagian Rebreather Course… a simple deconstruction

  1. Hi Ben, and thanks for the comment. Spares for servicing major bits and peices (first stages, hoses, fuel cells etc.) would be easy since it uses standard components Currently, replacement parts would have to come from Andy in Thailand… not sure but imagine as the unit become more common, there will be some sort of distributorship in UK or US.

  2. Hi Steve.

    I’m not sure if I mentioned this last time I wrote. To help with setting up the unit with 40s, I use a piece of plumbing pipe cut to length. I rest the srcubber cannister on it when setting up the tanks.

    It is lightweight and hollow so stuff can be packed inside it for travelling, it is about the same size as an SMB.

    I have a list of all spares for the unit if you need that I got off Andy. So it lists the BOV exhaust valves and diaphragm etc. Let me know if you want it and I’ll post it on here.


  3. Doppler

    Again, nice write up on the course. Last weekends dive on the unit went well, one more like that and I will have to remove the John Deere lable from your unit. 🙂


  4. Hi Doppler,

    Thank you very much for a very informative write up. This is one of the units I have singled out for purchase and if you have the time, I was wondering if you could commnet on
    *how you find diving with the Pelagian after your initial training?
    *have you made any modifactions to the unit or are you still diving it stock?
    *any build/quality issues
    *any maintenance issues

    It will be some time before I make a purchase as I am in research mode

    Many thanks for your comments


  5. Hi Doppler,
    Thanks for a great insight into diver training with the Pelagiac.Thinking of going to ccr from oc and its between inspiration vision and pelagiac.Would value your opinion.
    Regards JJ

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